1. Field of the Invention
This invention relates to an appliance that is fixed to a patient""s tooth during the course of orthodontic treatment. The appliance has a small retaining guide to hold a wire segment or another item connected to the appliance in place.
2. Description of the Related Art
Orthodontic treatment involves movement of malpositioned teeth to desired locations along the dental arches. Orthodontic treatment provides improved occlusion so that the teeth function better together during chewing. Orthodontic treatment can also greatly enhance the aesthetic appearance of the patient""s oral cavity by realigning crooked teeth and eliminating gaps or spaces between adjacent teeth.
One common form of orthodontic treatment is carried out by the use of tiny, slotted appliances known as brackets that are secured to the patient""s anterior, cuspid and bicuspid teeth. An archwire is received in the slot of the appliances and forms a track to guide movement of the teeth to desired positions. Ends of the archwires are often received in passageways of small appliances known as buccal tubes that are secured to the patient""s molar teeth.
Many orthodontic appliances have small, curved protrusions known as tiewings that extend outwardly from a central body of the appliance. For example, certain brackets have two spaced apart tiewings that extend in a gingival direction (i.e., a direction toward the patient""s gingiva or gums). Those brackets also often have two spaced apart tiewings that extend in an occlusal direction (i.e., in a direction toward the outer tips of the patient""s teeth). The gingival tiewings are connected to a central body of the bracket along a gingival side of the archwire slot and the occlusal tiewings are connected to the bracket body along an occlusal side of the archwire slot.
Tiewings are commonly used by the orthodontist during treatment to hold the archwire in the archwire slot. To this end, a ligature is placed along the back or lingual side of the occlusal tiewings and the gingival tiewings and is also placed over the front or labial side of the archwire. (As used herein, the word xe2x80x9clingualxe2x80x9d refers to a direction toward the patient""s tongue, while the word xe2x80x9clabialxe2x80x9d refers to a direction toward the patient""s lips or cheeks.) In many instances, the ligature holds the archwire in contact with the bottom or lingual side of the archwire slot. However, in instances where the tooth is significantly maloccluded and initially located some distance from the archwire, the ligature serves to urge the archwire in a direction toward the bottom of the archwire slot.
In general, there are two types of ligatures in widespread use. One type of ligature is in the form of a tiny elastomeric O-ring. The O-ring is sufficiently flexible such that it can be stretched around and behind the tiewings as well as over the front side of the archwire. Once the O-ring is in place, the inherent memory of the elastomeric material tends to return the O-ring toward its normally compact, unstretched configuration. This contracting force urges the archwire toward the bottom of the archwire slot and also helps to retain the ligature in place.
Other types of ligatures are known as wire ties. These ligatures are made from short lengths of wire such as stainless steel wire having a small cross-sectional diameter. In use, the orthodontic practitioner extends the wire ligature around the backs of the tiewings as well as across the front side of the archwire, and then twists the free ends of the ligature together. Once the ends are twisted together and any slack in the ligature has been removed, the archwire is retained in the archwire slot or is urged toward the same.
The tiewings of the orthodontic appliances described above typically have a concavity in the form of a curved groove or notch that extends along the lingual side of the tiewing. For example, many tiewings have a semi-cylindrical lingual concavity that is oriented such that the central axis of the semi-cylindrical shape is approximately parallel to the longitudinal axis of the archwire slot. In some instances, the opposite side (or labial side) of the tiewing is generally flat and co-planar with a labial side of the appliance body. In other instances, the labial side of the tiewing has a curved configuration complemental to the curved concavity of the lingual side, such that the tiewing has an overall, somewhat hook-shaped or xe2x80x9cCxe2x80x9d-shaped configuration.
The lingual concavity of the tiewings as described above is generally considered important since it helps to retain the ligature in place during the course of treatment. Ligatures that become detached from appliances in use represent a significant nuisance since they may be inadvertently swallowed by the patient. In addition, appliances that are no longer connected to archwires due to missing ligatures are ineffective in moving the associated tooth, and as a result the length of treatment time may be extended.
As a consequence, manufacturers of orthodontic appliances have often designed and constructed tiewings to reduce the likelihood that the ligature will become detached from the appliance during the course of treatment. To this end, the lingual concavity of the tiewings typically is sufficiently large to extend around a substantial portion (such as one-half) of the periphery of the ligature when considered in cross-sectional reference planes. Ligatures that are deeply seated in the concavity during use are less likely to slip off of the tiewing and become disengaged from the appliance.
However, ligatures are available in a wide variety of cross-sectional sizes and shapes. Wire ligatures typically have a round cross-sectional shape with diameters ranging from about 0.008 in. (0.20 mm) to about 0.014 in. (0.36 mm). Ligatures made from an elastomeric material often have a cross-sectional diameter that is much larger, such as about 0.030 in. (0.76 mm) when relaxed and about 0.020 in. (0.5 mm) when in use. Furthermore, elastomeric ligatures are also known having cross-sectional shapes other than circular (see, e.g., U.S. Pat. No. 3,758,947).
As a result, the tiewings of orthodontic appliances are often provided with relatively large lingual concavities in order to accommodate any one of the wide variety of ligature sizes that might be selected by the orthodontic practitioner. This large lingual concavity tends to increase the overall size of the tiewing. Furthermore, tiewings are also designed with relatively thick cross-sections so that they are less likely to fracture and break off from the body of the appliance during use. Strong tiewings are deemed important because the tiewings are sometimes subjected to large forces, such as when a tiewing encounters a relatively hard food object in the oral cavity while the patient is eating.
Consequently, the tiewings of orthodontic appliances are often bulky in relation to remaining structural aspects of the appliance. The relatively large size of the tiewings is considered a disadvantage, however, because it increases the likelihood of contact with opposing dentition or with appliances mounted on opposing dentition. Tiewings may also contact adjacent soft tissue in the oral cavity and cause an irritation.
Manufacturers of orthodontic appliances have sometimes omitted tiewings when designing buccal tubes. The archwire passageways of buccal tubes are often closed along four sides, in contrast to the archwire passageways or slots of orthodontic brackets that are open along one side. When the ends of the archwires are inserted in the closed passageways, ligatures for connecting the archwire to the buccal tube appliance are not needed. The elimination of tiewings from such appliances helps to ensure that the appliance does not unduly bear against other structure in the oral cavity.
However, there are some instances where orthodontic practitioners prefer to use a buccal tube appliance having tiewings. For example, some buccal tubes for first molar teeth have a passageway that can be opened along one side for converting the buccal tube to a bracket. Opening of the passageway is often carried out in adolescent patients after that patient""s adjacent second molar tooth has erupted sufficiently to receive a buccal tube on its surface. Once the passageway of the buccal tube on the first molar tooth has been opened, the tiewings serve to hold a ligature in place.
Additionally, there may be a gap between adjacent teeth at one or more locations along the dental arch. In those instances, the practitioner may elect to install a wire segment known as a xe2x80x9ctieback loopxe2x80x9d to move teeth along the length of the arch and close the gap. Typically, one side of the tieback loop is connected to a buccal tube, while the opposite side of the loop is connected to an appliance that is located on the opposite side of the gap.
Some practitioners prefer to connect tieback loops to a hook of the buccal tube appliance. However, other practitioners prefer to connect tieback loops to the body of the buccal tube appliance. In those instances, the loop extends along the occlusal, distal and gingival sides of the buccal tube body in a location next to the base. Once the ends of the tieback loop are twisted together to remove slack, the tiewings help ensure that the loop does not slip off the body. Unfortunately, the tiewings are often considered troublesome for the reasons mentioned above.
In the past, a rear portion of some buccal tube appliances extends in a distal direction (i.e., in a direction away from the center of the patient""s dental arch) in spaced, overhanging relation to the base. This overhanging portion presents a notch adjacent the base of the appliance which can be used to receive a tieback loop. However, the notch is often considered unsatisfactory, since the tieback loop when received in the notch interferes with an archwire extending through the archwire passageway.
At present, there is a need in the art for an orthodontic appliance having improved features for securely retaining tieback loops and other items in place as needed. Preferably, such an appliance has an overall relatively compact configuration to reduce the likelihood that it might contact the opposing teeth of the other dental arch, bear against orthodontic appliances that are mounted on the opposing teeth or irritate adjacent soft tissue.
The present invention is directed to an orthodontic appliance with a contoured retaining guide that presents a low profile. The retaining guide functions to keep a wire segment or other item in place during the course of treatment. Preferably, the retaining guide is smoothly curved and lacks any substantial recess or concavity that might otherwise trap food particles and other debris.
The retaining guide of the present invention is particularly useful for keeping a tieback loop in a proper orientation on the appliance and in a securely coupled relationship to the appliance. Examples of suitable appliances include buccal tube appliances, bracket appliances and self-ligating appliances, including appliances that lack tiewings as well as appliances that have tiewings. Preferably, the retaining guide has an outer domed surface that slopes gradually from adjacent surfaces of the appliance body. The guide also preferably has a gently rounded, low profile outer edge that reduces the likelihood of interference with other structure in the oral cavity.
In more detail, the present invention is directed in one aspect to an orthodontic appliance that comprises a base and a body extending outwardly from the base. The body has an occlusal side, labial side and a gingival side. The body also has a mesial end and a distal end. The appliance further includes an elongated archwire passageway for receiving an archwire, and a guide extending away from the body for retaining a wire segment or other item in place. The guide is connected to one of the occlusal side and the gingival side of the body. The guide has an overall dome-shaped configuration when viewed in a direction toward the base.
Another aspect of the present invention is also directed toward an orthodontic appliance that comprises a base and a body extending from the base. The body has an occlusal side, a labial side and a gingival side. The appliance also includes an elongated archwire passageway for receiving an archwire, and a guide extending away from the body. The guide is connected to one of the occlusal side and the gingival side of the body. The guide has an outer edge section remote from the body and extends in a mesial-distal direction a certain distance. This certain distance increases in size as the outer edge section is approached.
A further aspect of the present invention also directed toward an orthodontic appliance. The appliance according to this aspect has a base and a body extending outwardly from the base. The body has an occlusal side, a labial side and a gingival side. The appliance also includes an elongated archway passageway for receiving an archwire, and a guide extending away from the body for retaining a wire segment or other item in place. The guide is connected to one of the occlusal side and the gingival side of the body and has an outer edge section remote from such side. The outer edge section when viewed in a lingual direction extends along a path that does not exceed an angle of 45 degrees with respect to the certain side.
An additional aspect of the invention is also directed to an orthodontic appliance that has a base and a body extending outwardly from the base. The body has an occlusal side, a labial side and a gingival side. The appliance additionally includes an elongated archwire passageway for receiving an archwire. A retaining guide extends away from the body and is connected to one of the occlusal side and the gingival side of the body. The guide has an overall generally triangular configuration when viewed in a direction toward the body along a generally occlusal-gingival reference axis.
These and other aspects of the invention are described in more detail below and are illustrated in the accompanying drawings.